How much epoxy resin do you need?

Calculate the space you intend to fill

Epoxy quantity starts with geometry. For a rectangular region, multiply length by width by the intended resin thickness. Use one unit throughout the calculation. Dimensions in centimeters produce cubic centimeters; one cubic centimeter equals one milliliter. Dimensions in inches produce cubic inches; divide by 231 for US gallons.

Use resin thickness, not the thickness of the board beneath it. For a coating, measure the finished film you are planning within the product’s application limits. For a mold, measure the internal cavity. Record whether your result includes only the main pour or also seal coats and finishing coats.

Work a simple example

A rectangular mold measuring 20 cm by 10 cm with a planned 0.5 cm fill requires 100 cubic centimeters, or 100 mL, before accounting for inserts and handling losses. This is the total mixed volume. It does not mean 100 mL of resin plus an additional amount of hardener.

A circular mold uses pi multiplied by radius squared multiplied by depth. A 10 cm diameter cavity filled 0.5 cm deep has a geometric volume of approximately 39.3 mL. The radius is half the diameter; confusing these measurements makes the estimate four times too large. Rounded walls, tapered molds and raised details require adjustments.

Compare a relevant resin kit

TotalBoat TableTop: check the selected 1 gallon kit, included components and current offer. Read the formula limits before choosing it for your project.

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Read formula notes and other kit sizes

Estimate an irregular river in sections

A natural wood edge rarely makes a perfect rectangle. Divide the river length into short sections, measure the width at each section boundary and use the average of adjacent widths for that section. Multiply each section’s length, average width and depth, then add the results. More measurements around sharp changes improve the estimate.

Count connected knots, cracks and voids separately if they are not captured by the river outline. Subtract the volume occupied by substantial embedded objects only when you can estimate it credibly. For delicate or porous inclusions, using a cautious purchasing allowance is often more practical than trying to measure exact displacement.

Keep allowances visible

Create separate lines for main fill, seal coat, planned finishing coat, edge runoff and material left in cups. There is no universal waste percentage that accurately describes all these jobs. A contained mold and a coating that flows over four edges have very different losses.

Choose a modest contingency appropriate to the uncertainty and label it clearly. Reserve material does not all need to be mixed at once. Purchase enough for the project, then divide the work into manufacturer-approved batch sizes. An accurate total-volume estimate does not authorize a single batch or a single deep pour.

• Flat mold: check internal dimensions and subtract known solid inserts.
• Edge-flow coating: budget separately for runoff and the seal coat.
• River table: measure varying widths, connected cavities and finishing allowance.
• Repeated pieces: estimate one cavity, multiply by the count, then add shared handling losses.

Translate the result into a kit and batch plan

Check whether a kit’s advertised amount is the combined resin and hardener or one component alone. To divide mixed volume into components, use the product’s stated volume ratio. To weigh components, use its specified weight ratio and product density information when converting from a volume target. Milliliters and grams are not interchangeable.

Before opening the bottles, write the target for each component and each batch. Include the ratio basis and units on the sheet. After the project, compare estimated use with actual use and note where the difference occurred. Those notes improve the next estimate far more than silently increasing every project by the same percentage.